Electrical conductors with strippable polymeric materials

ABSTRACT

A composite of polymeric materials which are adheringly joined to each other and which can be easily and cleanly separated by stripping apart with a low pulling force whereupon the contacting surfaces of their interface each separate cleanly without retention of any residue from the other, and which comprises the combination of a body of peroxide curable ethylene-containing polymer adjoined to a body of a sulfur curable elastomer comprising chlorosulfonated polyethylene. The combination of materials is especially advantageous when used in wire and cable constructions comprising a composite of an electrical insulation and an overlying strippable semiconductive layer.

United States Patent Betts et a1.

ELECTRICAL CONDUCTORS WITH STRIPPABLE POLYMERIC MATERIALS [451 Sept. 30,1975 3,793,476 2/1974 Misiura 174/120 SR Primary Examiner-E. A. GoldbergAttorney, Agent, or FirmR. G. Simkins; P. L. Schlamp; F. L. Ncuhauser 57 ABSTRACT A composite of polymeric materials which are adheringlyjoined to each other and which can be easily and cleanly separated bystripping apart with a low pulling force whereupon the contactingsurfaces of their interface each separate cleanly without retention ofany residue from the other, and which comprises the combination of abody of peroxide curable ethylenecontaining polymer adjoined to a bodyof a sulfur curable elastomer comprising chlorosulfonated polyethylene.The combination of materials is especially advantageous when used inwire and cable constructions comprising a composite of an electricalinsulation and an overlying strippable semiconductive layer.

10 Claims, 2 Drawing Figures fiZ'lP'SFZ? "SUL H OROSULFONATED CFOLYETHYLENE EROXIDE-CURED l2 E'FHYLENE-CONTAINING POLYMER INSULA TI ONUS. Patent Sept. 30,1975 3,909,507

ELECTRICAL CONDUCTORS WITH STRIPPABLE POLYMERIC MATERIALS .CROSSREFERENCE TO RELATED APPLICATION This application is related to US.application Ser.

7 No. 336,146, filed Feb. 26, 1973, for Insulated Conductor WithStrippable Layer, by Thaddeus Misiura and Joseph E. Vostovich, now US.Pat. No. 3,793,476,

and assigned to the same assignee as this application.

BACKGROUND OF THE INVENTION A common type of construction for electricalwires or cables designed for medium to high voltage applications, forexample about to 35 KV, as well as other classes of electrical service,comprises combinations of one or more insulating layers andsemiconductive layers. In a typical cable structure, for instance, themetallic conductor may be provided with an organic polymeric insulationsuch as cross-linked polyethylene, and ;an overlying body ofsemiconducting material comprising an organic polymeric compositionwhich has been rendered electroconductive by the inclusion therein ofelectrical conductivity imparting agents or fillers such as carbonblack. Although these cable constructions may vary in certain elements,and often include an intermediate component disposed between themetallic conductor and the primary body of dielectric insulation such asa layer of separating tape or inner layer of semi conductive material,or are enclosed within protective covering sheaths, all such cableconstructions conventionally include therein at least a body of primaryinsulation surrounding theconductor with an overlying body ofsemiconducting material in physical contact with the insulation.However, 'this arrangement of a layer of insulation with a superimposedlayer of semiconductive material thereover incurs certain handicaps.

,face between the adjoining surfaces of the body of the insulation andthe body of semiconducting material. US. Pat. No. 3,677,849 deals withthis problem of intermediate void spaces at the interface of theinsulation and semiconductive material by applying a heat treatment tothe assembled product to induce a shrinkage of the semiconductivematerial tightly about the insulation. US. Pat. No. 3,259,688 proposes adifferent solution to this problem comprising a distinctive construction and an irradiation treatment. Further, U.S. Pat.

No. 3,646,248 discloses that this problem is resolved by the use of anolefinic terpolymer insulation with a first curing system and anolefinic terpolymer semiconductive material with a second curing systemcomprising a different curing agent.

Further, the insulation layer and overlying semiconductive layer forelectrical cable can be formed concurrently about the wire or metalconductor by means of a continuous simultaneous extrusion process withone Iextruder apparatus, or these layers are formed in sequenceemploying tandem extruders, and both layers are thereafter cured at thesame time in a single operation and unit to minimize manufacturing stepsand apparatus. However, the simultaneous curing of both la'yerstogether, or even the curing of only one layer alone while it is in acontiguous arrangement. with the other, can result in the apparentformation of cross-linking bonds bridging the interface between theadjoining surfaces of each phase. The occurrence of such crosslinkingbonds bridging the interface between the surfaces of said phases rendersvery difficult their subsequent separation, such as in the removal of aportion of the body of semiconductive material from about the insulationby stripping for the purpose of making cable splices or terminalconnections. Such separation requires the application of great force,and, upon being peeled off, the semiconductive material is prone toleaving a substantial residue of its mass firmly adhering to the othersurface or insulation. As is known in the art, it is necessary whensplicing and treating cable ends that the semiconductive material becleanly stripped or completely removed from the terminal section of thecable end without any damage or material loss to the underlying surfacesof the insulation, and thus the separation can require an appreciableamount of added labor time and costs when the semiconductive material isdifficult to remove by stripping and/or a residue thereof is retainedtanaciously adhering to the surface of the insulation. The difficultiesof this aspect of such cable constructions are the subject of US. Pat.Nos. 3,684,821 and 3,643,004.

SUMMARY OF. THE INVENTION This invention comprises a combination ofspecific organic polymeric materials, which are cured with dissimilarcuring systems, and a composite construction formed therewith whereinthe two phases or bodies of the curable materials are adheringly unitedwith each other at their abutting surfaces to provide a substantiallycontinuous and secure union of their contacting surfaces extending overtheir common interface. The combination and cure systems of theinvention effectively obviate the occurrence of intermediate void spacesbetween the interface of the two phases or bodies, while at the sametime providing an interface union between the phases which is easilyseparated with a relatively small pulling force whereupon the componentspart with clean surfaces each free of any residue from the other. Theinvention also comprises a method of producing electrically insulatedand shielded cables.

The invention includes the combination of a first body of peroxidecurable ethylene-containing polymer with a second body composed of asulfur curable chlorosulfonated polyethylene rubber (Hypalon). Thesulfur curable chlorosulfonated polyethylene can contain minor amountsof an ethylene-propylene rubber dispersed therethrough to enhance theplastic properties of the chlorosulfonated polyethylene rubber.

The compositions and the attributes of this combination are uniquelysuitable and advantageous for use in the construction of insulatedelectrical wires and cables in the formation of a composite insulationof an ethylene-containing polymer with an easily and cleanly strippablesemiconductive material superimposed over the insulation. The polymericmaterial comprising the said chlorosulfonated polyethylene elastomer canbe rendered suitably electroconductive so as to perform as asemiconductive material by appropriately filling it with a typicalelectrical conductivity imparting agent or filler such as carbon black,dispersed therethrough, or some other electrically conductiveparticulate material amounts so as to impart the desired degree ofconductivity.

OBJECTS OF THE INVENTION It is a primary object of this invention toprovide curable polymeric materials that can be joined in a contiguousrelationship with their interfacial surfaces adheringly united togetherso as to eliminate the presence or any occurrence of intermediate voidspaces therebetween, and which thereafter can be separated by theapplication of a very low pulling force with the interfacial surfaces ofthe bodies cleaving cleanly and free of any adhering residual material.

It is also a primary object of this invention to provide insulativeelectrical conductors or wire with coverings including a combination ofbodies of cured organic polymeric materials comprising a first layer ofinsulation with a surface thereof adheringly joined to a surface of asecond layer which may be of any suitable thickness down to less thanabout 1 millimeter, and wherein the second layer of the polymericmaterial is easily and cleanly strippable from the first layer ofinsulation with a very low peeling effort of only a few pounds pullingforce per /2 inch wide strip of material, leaving the separated surfaceof each layer intact, and clean and free of any residue, and a method ofmaking the same.

It is an additional and specific object of this invention to provide aninsulated electrical wire or cable having a multilayered covering abouta metallic conductor comprising a combination of cured polymericmaterials consisting of an insulation and an overlying semiconductiveshield which is free of intermediate voids or spaces at the interface ofsaid materials, and wherein the material consisting of thesemiconductive shield comprising a polymeric carrier or matrix forparticulate conductive filler material dispersed therethrough can bepeeled or stripped off the underlying insulation with little effort orpull and it separates or parts cleanly from the surface of theinsulation leaving it intact and without adhering material, and a methodof making the same.

It is a further object of this invention to provide a curable compositepolymer system of two layers or bodies which can be substantiallysimultaneously formed and joined together such as in a dual-headextruder and simultaneously cured joined in intimate physical contactwith each other, and the thus formed layers or bodies can thereafter becleanly separated or stripped apart with a very small effort or force.

BRIEF DESCRIPTION OF THE DRAWING FIG. 1 comprises a perspective view ofa portion of an insulated conductor having a semiconductive shieldDESCRIPTION OF A PREFERRED EMBODIMENT This invention is hereinafterdescribed in relation to its principal field of application and utility,namely, the

construction and method of producing electrical wire and cable, althoughother areas of application are contemplated.

The invention specifically comprises a novel combination of givencurable polymeric materials, or com bined bodies composed. thereof,which provide unique interfacial characteristics when their contiguoussurfaces are adheringly joined together by curing the polymeric materialof at least one of the combined bodies. Curable polymeric materials ofthe invention comprise v for the one phase, a body or unit of peroxidecurable ethylene-containing polymer, and for the other phase of thecomposite, a body or unit of a sulfur curable chlorosulfonatedpolyethylene elastomer.

The peroxide curable ethylene-containing polymer of one phase of thecombined polymeric bodies includes polyethylene, a common andextensively used electrical insulation material for wire and cable,which is cross-link curable with peroxide curing agents to a thermosetstate in keeping with the requirements of the invention. Also includedare similar copolymers of ethylene and other polymerizable materials,and blends of such polymers and copolymers which are atleastpredominantly composed of ethylene and are known in the art to provideeffective cross-link curable electrical insulations. For example,copolymers of ethylene and' vinyl acetate and similar copolymers whereinthe ethylene content is a majority of more than 50% by weight,

and preferably at least about by weightof ethylene content. The latterclass of copolymers of ethylene and blends for electrical insulatingmaterials for wire and cable are disclosed in the above mentioned U .8.Pat. Nos. 3,259,688 and 3,684,821, and other prior art publications.

The sulfur curable. chlorosulfonated polyethylene (I-lypalon) elastomerphase, which when joined with the peroxide curable ethylene-containingpolymer phase together produce the distinctive interfacialcharacteristics and functions of this invention, may include minoramounts of an ehtylene-propylene copolymer or terpolymer rubber as asoftening agent or plasticizer to render the chlorosulfonatedpolyethylene more tractable in compounding with the electroconductivefiller and other ingredients and in processing and forming. Beingcurable with the same sulfur curing systems as the chlorosulfonatedpolyethylene, the terpolymers of ethylene, propylene and a diene can beincluded in amounts of up to about 30 by weight of the blend with thechlorodulfonated polyethylene. The copolymers of ethylene and propylenewhich are not curable with sulfur systems, cannot be tolerated inproportions of more than about 20% by weight of the blend with thechlorosulfonated polyethylene elastomer. Terpolyme rs ofethylene-propylene include commercially available rubbers produced bythe copolymerization of ethylene and propylene together with minorproportions of dienes such as ethylidiene norbornene, or dicyclopen- ISulfur-bearing curing systems for the chlorosulfo.- nated polyethylene(Hypalon), and ethylene-propylene terpolymers, are conventional and wellknown in the art, for

example, tetrainethylthiuram disultide (METHYL TUADS), tetraethylthiuramdisulfide (ETHYL TUADS), dipentamethylene thiuram tetrasulfide(SULFADS), and the like commercial sulfur bearing curing agents.

For service in electrical applications such as a semiconductivecomponent in cable for medium to high voltage service, the sulfurcurable chlorosulfonated polyethylene elastomer can be easily renderedelectroconductive to any appropriate degree desired by the filling orinclusion therethroughout of a suitable amount of an electricalconductivity imparting agent, such as about to 75 parts of carbon blackor metal particles by weight of the polymeric ingredients according toconventional practices. When aptly rendered electroconductive with asuitable amount of a conductive material, dispersed therethroughout, thechlorosulfonated polyethylene can fulfill the required electricalfunctions of a semiconducting material in electrical cable, and whencombined with an ethylenecontaining polymer insulation and cured inaccordance with requirements of this invention, it provides the uniqueinterfacial properties which effectively eliminate the occurrence ofintermediate void spaces between the interfaces of insulation andsemiconductive materials and also enables an easy and clean separationof the semiconductive material from the insulation.

The ethylene-containing polymeric material or phase of the combinationof this invention is curable to a substantially thermoset condition bycross-linking with a free radical forming peroxide according toconventional practices such as described in U.S. Pat. Nos. 2,888,424 and3,079,370, and subsequent relevant prior art. A preferred cross-linkingcuring system for the ethylene-containing polymeric material comprisesthe use of a tertiary peroxide curing agent such as a dicumyl peroxide.

in the practice of this invention it is required that at least one ofthe polymeric bodies or phases, either the peroxide curableethylene-containing polymer or the sulfur curable chlorosulfonatedpolyethylene, undergoes curing while the surface thereof is in intimatephysical contact with the surface of the other polymeric body or phasewhereby the curing mechanism of one phase can effect the apparent bondsbridging the surfaces to adheringly unite the contacting surfaces of theinterface. However, as a practical matter the most expedientmanufacturing systems such as the sequential or tandem extrusion of thedual layers of ethylenecontaining polymer and overlying chlorosulfonatedpolyethylene upon the wire core followed by simulta-' neous curing ofboth phase together, would incur the preferred curing of each polymericphase or material of the combination at the same time to achieve theoptimum effects thereof.

Referring to the drawing, a typical cable of mediumto-high voltagecapacity of the type to which this invention is especially applicableand advantageous, is shown in perspective in FIG. 1, and a short portionof such a 'cable is also shown with the insulation and semiconductivelayer in longitudinal cross section about the conductor in FIG. 2. Theoverall cable product 10, primarily comprises a metallic conductor 12, arelatively thick first body ofa peroxide cured ethylene-containingpolymeric insulation 14 surrounding the conductor; and overlying theinsulation is a second body or layer of a sulfur cured chlorosulfonatedpolyethylene semiconductive material 16. Other components can be included in the cable structure following known designs,

for example separating paper or tape, or a semiconductive layer locatedbetween the metallic conductor 12 and the primary insulation 14, such asare shown in the aforementioned U.S. Pat. Nos. 3,259,688 and 3,684,821,and the means of this invention apply thereto with its attendantadvantages whenever the insulation abuts the semiconductive component,as is conventional in medium-to-high voltage capacity cables. Uponcuring at least one component of the superimposed combination, eitherthe body of the peroxide curable ethylene-containing polymer insulation14 or the body of the sulfur curable chlorosulfonated polyethylene,filled semiconductive material 16, and preferably both together, theinsulation and semiconductive material covering the insulation becomeadheringly joined to each other producing a united interface 18 ofunique attributes which eliminate intermediate voids. Moreover, the thusformed adhering bond between these components can be separated upon theapplication of a small pulling force of only a few pounds and thesurfaces at the interface separate cleanly leaving each surface free ofadherents from the other.

The following comprise specific examples of suitable and preferredpolymeric materials for the application of this invention in theconstruction of high-voltage cable comprising a body of peroxide curablepolyethylene insulation combined with an overlying body ofsemiconductive material of a polymeric carrier or matrix comprisingsulfur curable chlorosulfonated polyethylene elastomer filled withparticulate conductive material.

The ethylene-containing polymer composition comprising the insulation,or one phase or polymeric body of the combination of this invention,consisted of the following typical commercial insulating formula:

di 0:- cumyl peroxide These ingredients were compounded in a suitablemixer comprising a roll mill, until substantially homogeneouslydispersed. However, pursuant to conventional practices, all ingredients,except for the peroxide, were first admixed at elevated temperatures ofabout 250F, or within a range of about 200F to 300F, to flux the polymerand expedite the mixing. Thereafter the mix was cooled to below thedecomposition temperature of the particular peroxide curing agent, inthis case down to below about 220F, whereupon the peroxide curing agentwas added and dispersed through the mix. The compound was then ready forforming to a given shape and curing by the application of heat.

The following comprises examples of the sulfurcured chlorosulfonatedpolyethylene elastomer, which as a body or layer in combination with abody or layer of peroxide-cured ethylene-containing polymer, producesthe unique interface characteristics of this invention. In theseexamples the sulfur curable chlorosulfonated polyethylene component isfilled with an electrically conductive carbon black for the purpose ofpereach of the specimens were found to separate clean and free of anyresidue.

INGREDIENTS EXAMPLES Chlorosulfonated polyethyleneduPont, Hypalon 40S100.0 70.0 80.0 90.0 Ethylene-propylene terpolymer-duPont, Nordel 132030.0 20.0 10.0 Conducting carbon black-Cabot, Vulcan XC-72 45.0 45.045.0 45.0 Hydrocarbon processing oil-Sun Oil, Circosol 4240 17.0 17.017,0 17.0 Litharge (90%) in ethylene-propylene binder-TLD-90 20.0 20.020.0 20.0 Microcrystalline wax Sunoco Anti-Chek 2.0 2.0 2.0 2.0Antioxidant-dihydro-trimethylquincline-Vanderbilt, 0.5 0.5 1 1.0

Agerite Resin D N,N'-m-phenylenedimaleimide duPont HVA-2 0.5 0.6 0.5 0.5Curing agent-dipentamethylene thiuram hexasulfide- 0.6 0.6 0.6 0.6

Vanderbilt, Sulfads Approximate force in pounds needed to strip curedHypalon composition from cured polyethylene composition of Example A.0.78 1.58 2.4 2.1

forming as a semiconductive material in an electrical cable incombination with a polyethylene insulation of the above formulation.

EXAMPLES l IV In the following examples, samples composed of theperoxide curable polyethylene composition given in Example A, and asample of sulfur curable chlorosulfonated polyethylene elastomer and ablend thereof with an ethylenepropylene terpolymer formulation given inExamples 1 and 11 were individually sheeted on a hot mill, and a warmstrip, measuring about 0.060 to 0.075 inch thickness, of thepolyethylene composition was combined with a similar warm strip of eachone of the formulations of Examples 1 and II of about the samethickness. The thus formed combined strip specimens comprising compositeExamples A-1 and A-ll were each individually molded as composite slabsin a press and cured at 310F for about 45 minutes to simulate asequential extrusion molding of one warm layer upon the other followedby a simultaneous curing.

Upon cooling each specimen to room temperature and conditioning each atambient conditions for approximately 16 hours, a 4 inch long and V2 inchwide section of each composite cured specimen was tested in a Scotttester for strippability, and the pulling force in pounds required toseparate the adhering layers of each specimen is given in the followingtable for Examples I and II.

The formulations given in Examples Ill and IV, were respectivelyextruded in a thickness of about 0.045 inch over an uncured polyethyleneinsulation of the composition of Example A which had been formed with anextruder around a core of a number 20 AWG wire conductor in a thicknessof about 0.175 inch. Each of said wire specimens of the composite ofperoxide curable polyethylene and sulfur curable chlorosulfonatedpolyethylene blends were then cured with steam at a temperature of about210 psig (392F) for a dwell period of about 3 minutes. After cooling andconditioning at room temperature the pull required for stripping orseparating the layer of each sample of polymer composite and its partingcharacteristics were determined. The pulling force to strip a one halfinch wide section of the chlorosulfonated polyethylene formulation givenin Examples 111 and 1V from the adhesively joined polyethylenecomposition of Example A is also given in the following Table forExamples IlV. Also We claim:

1. An insulated metallic electrical conductor having a covering thereoncomprising, a combination of polymeric compositions including acomposite of an electrically-insulating body of a peroxide-cured productofan ethylene-containing polymer with a surface adheringly joined to acontacting surface of an easily and cleanly strippable overlyingsemi-conductive body of a sulfurcured product of an elastomer ofchlorosulfonated polyethylene, with said contacting surfaces of theinsulating body and overlying semiconductive body being adheringlyjoined to each other as a result of at least one of said polymericmaterials having been cured while the said surfaces of each of thebodies are in adjoining physical contact with each other.

2. The insulated metallic electrical conductor of claim 1, wherein thesaid contacting surfaces of the insulating body and overlyingsemiconductive body are adheringly joined to each other as a result ofboth the ethylene-containing polymer and the elastomer ofchlorosulfonated polyethylene having been cured simultaneously while thesurfaces of their bodies are in adjoining physical contact with eachother.

3. The insulated metallic electrical conductor of claim 1, wherein thebody of the sulfur-cured product of an elastomer of chlorosulfonatedpolyethylene contains an electrically conductive filler dispersedtherethroughout.

4. The insulated metallic electrical conductor of claim 3, wherein theelectrically conductive filler is present in an amount of about 15 toabout by weight of the chlorosulfonated polyethylene elastomer.

5. The insulated metallic electrical conductor of claim 3, wherein theelectrical conductive filler comprises carbon black.

6. The insulated metallic electrical conductor of claim 1, wherein thesemiconductive body of a sulfurcured product of an elastomer ofchlorosulfonated polyethylene includes up to about 30% by weight of anethylenepropylene terpolymer.

7. The insulated metallic electrical conductor of claim 1, wherein thesemiconductive body of a sulfurcured product of an elastomer ofchlorosulfonated polyethylene includes up to about 20% by weight of anethylene-propylene copolymer.

8. The insulated metallic electrical conductor of claim 1, wherein theelectrically insulating body of a peroxide-cured product of anethylene-containing polymer is polyethylene cured with an organictertiary peroxide curing agent.

9. An insulated metallic electrical conductor having a covering thereoncomprising, a combination of polymeric compositions including acomposite of an electrically insulating body of a peroxide-cured productof polyethylene and an organic tertiary peroxide curing agent, with asurface thereof adheringly joined to a contacting surface of an easilyand cleanly strippable overlying semiconductive body of a sulfur-curedproduct of an elastomer of chlorosulfonated polyethylene and asulfur-containing curing agent having an electrically conductive fillerdispersed therethroughout in an amount of about to about 75% by weightof the clastomer, said contacting surfaces of the insulating body yleneand propylene.

1. AN INSULATED METALLIC ELECTRICAL CONDUCTOR HAVING A COVERING THEEONCOMPRISING A COMBINATION OF POLYMERIC COMPOSITION INCLUDING A COMPOSITEOF AN ELECTRICALLY-INSULATING BODY OF A PEROXIDE-CURED PRODUCT OF ANETHYLENE-CONTAINING POLYMER WITH A SURFACE ADHERINGLY JOINED TO ACONTACTING SURFACE OF AN EASILY AND CLEANLY STRIPPABLE OVERLYINGSEMI-CONDUCTIVE BODY OF A SULFUR-CURED PRODUCT OF AN ELASTOMER OFCHOROSULFONATED POLYETHYLENE WITH SAID CONTACTING SURFACES OF THEINSULATING BODY AND OVERLYING SEMICONDUCTIVE BODY BEING ADHERINGLYJOINED TO EACH OTHER AS A RESULTOF AT LEAST ONE OF SAID POLYMERICMATERALS HAVING BEEN CURED WHILE THE SAID SURFACES OF EACH OF THE BODIESARE IN ADJOINING PHYSICAL CONTACT WITH EACH OTHER.
 2. The insulatedmetallic electrical conductor of claim 1, wherein the said contactingsurfaces of the insulating body and overlying semiconductive body areadheringly joined to each other as a result of both theethylene-containing polymer and the elastomer of chlorosulfonatedpolyethylene having been cured simultaneously while the surfaces oftheir bodies are in adjoining physical contact with each other.
 3. Theinsulated metallic electrical conductor of claim 1, wherein the body ofthe sulfur-cured product of an elastomer of chlorosulfonatedpolyethylene contains an electrically conductive filler dispersedtherethroughout.
 4. The insulated metallic electrical conductor of claim3, wherein the electrically conductive filler is present in an amount ofabout 15 to about 75% by weight of the chlorosulfonated polyethyleneelastomer.
 5. The insulated metallic electrical conductor of claim 3,wherein the electrical conductive filler comprises carbon black.
 6. Theinsulated metallic electrical conductor of claim 1, wherein thesemiconductive body of a sulfur-cured product of an elastomer ofchlorosulfonated polyethylene includes up to about 30% by weight of anethylenepropylene terpolymer.
 7. The insulated metallic electricalconductor of claim 1, wherein the semiconductive body of a sulfur-curedproduct of an elastomer of chlorosulfonated polyethylene includes up toabout 20% by weight of an ethylene-propylene copolymer.
 8. The insulatedmetallic electrical conductor of claim 1, wherein the electricallyinsulating body of a peroxide-cured product of an ethylene-containingpolymer is polyethylene cured with an organic tertiary peroxide curingagent.
 9. An insulated metallic electrical conductor having a coveringthereon comprising, a combination of polymeric Compositions including acomposite of an electrically insulating body of a peroxide-cured productof polyethylene and an organic tertiary peroxide curing agent, with asurface thereof adheringly joined to a contacting surface of an easilyand cleanly strippable overlying semiconductive body of a sulfur-curedproduct of an elastomer of chlorosulfonated polyethylene and asulfur-containing curing agent having an electrically conductive fillerdispersed therethroughout in an amount of about 15 to about 75% byweight of the elastomer, said contacting surfaces of the insulating bodyand overlying semiconductive body being adheringly joined to each otheras a result of both the polyethylene and the elastomer ofchlorosulfonated polyethylene having been cured simultaneously while thesurfaces of their bodies are in adjoining physical contact with eachother.
 10. The insulated metallic electrical conductor of claim 9,wherein the semiconductive body of a sulfur-cured product of anelastomer of chlorosulfonated polyethylene includes up to about 20% byweight of at least one ethylene-propylene rubber selected from the groupconsisting of copolymers and terpolymers of ethylene and propylene.